LeetCode 702 - Search in a Sorted Array of Unknown Size

https://github.com/jiadaizhao/LeetCode/tree/master/0702-Search%20in%20a%20Sorted%20Array%20of%20Unknown%20Size

Given an integer array sorted in ascending order, write a function to search target in nums. If target exists, then return its index, otherwise return -1. However, the array size is unknown to you. You may only access the array using an ArrayReader interface, where ArrayReader.get(k) returns the element of the array at index k (0-indexed).

You may assume all integers in the array are less than 10000, and if you access the array out of bounds, ArrayReader.get will return 2147483647.

Example 1:

Input: array = [-1,0,3,5,9,12], target = 9
Output: 4
Explanation: 9 exists in nums and its index is 4

Example 2:

Input: array = [-1,0,3,5,9,12], target = 2
Output: -1
Explanation: 2 does not exist in nums so return -1

Note:

1. You may assume that all elements in the array are unique.
2. The value of each element in the array will be in the range [-9999, 9999].

Companies: Google

    int search(const ArrayReader& reader, int target) {
        int hi = 1;
        while (reader.get(hi) < target) {
            hi <<= 1;
        }
        int lo = hi >> 1;
        while (lo <= hi) {
            int mid = lo + (hi - lo) / 2;
            int val = reader.get(mid);
            if (val == target) {
                return mid;
            }
            else if (val < target) {
                lo = mid + 1;
            }
            else {
                hi = mid - 1;
            }
        }
        return -1;
    }
http://www.ardendertat.com/2011/11/21/programming-interview-questions-17-search-unknown-length-array/